2564643991 has 16 divisors (see below), whose sum is σ = 3162578944. Its totient is φ = 2025251424.

The previous prime is 2564643979. The next prime is 2564644009. The reversal of 2564643991 is 1993464652.

It is not a de Polignac number, because 2564643991 - 2⁹ = 2564643479 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2564643941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20650 + ... + 74536.

It is an arithmetic number, because the mean of its divisors is an integer number (197661184).

Almost surely, 2^2564643991 is an apocalyptic number.

2564643991 is a deficient number, since it is larger than the sum of its proper divisors (597934953).

2564643991 is a wasteful number, since it uses less digits than its factorization.

2564643991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54430.

The product of its digits is 1399680, while the sum is 49.

The square root of 2564643991 is about 50642.3142342449. The cubic root of 2564643991 is about 1368.8074569099.

The spelling of 2564643991 in words is "two billion, five hundred sixty-four million, six hundred forty-three thousand, nine hundred ninety-one".